Data accumulated during this current year indicated that the age-associated structural changes reported last year in aldolase of liver were not consistent, i.e., they were present in only one out of four studies carried out. Therefore, it was felt advisable to refect this model system to test the hypothesis that dietary restriction increases life span by reducing the use of the genetic code and thereby minimizing genetic imperfections as they may occur in late life. Instead, efforts have been made during the past year to establish two invertebrate systems which have been employed in studies concerning the relationship among dietary restriction, aging, and age-associated enzymatic structural changes. These systems are the rotifer and the nematode. Under our culturing conditions the life span and egg production of the rotifer, as well as the population density of the nematode, are in agreement with those found in the current literature. Three groups of animals ages 30 days, 14 months, and 20 months were fed varying amounts of vitamins. The results thus far indicate that feeding these amounts of vitamins to 20 month old mice has no effect on longevity. No data is presently available on the longevity of the younger groups of animals.